Prior to the present invention, stamping dies sets have been provided with pins and other guide devices to insure that the dies making the parts are in accurate alignment and with gaging blocks to insure that the blank or part being stamped is properly located in the die set so the stamped part meets specifications. While prior constructions and gaging procedures provide for quality stampings, the prior pins, gaging blocks and other devices for ensuring accuracy in stamped parts, particularly those produced with multiple die sets, may become worn or damaged to such an extent that the stamped parts produced by such die sets fail to meet specifications so that they have to be reworked or scraped.
With such problems being encountered with increasing frequency and with the demand and requirement for more precisely produced parts, the present invention addresses and solves a wide range of out of spec stampings by the provision of new and improved statistical process control tooling preferably in the form of cooperative bottoming markers in the die sets of multiple station dies to insure the dies that are making the parts are in the home position and that the part meets stamping specifications.
In one preferred form and embodiment of the invention, a different marker is placed in a predetermined location in each die set so that at the end of the stamping operation in which a part is made, marks made on the stamped part relate to one another to define a configuration to visually inform an inspector whether or not the part meets specifications. Importantly, if the part does not fall within specifications, the press line operator or other inspector is able to immediately note that the part produced is out of specification and be advised by the mark which die sets need to be adjusted or repaired so that parts can be subsequently stamped with the required accuracy for acceptance.
Importantly, the preferred embodiment of the invention employs sets or series of bottoming markers that visibly mark, coin or otherwise produce visible patterns such as concentric circles in the part as it is being progressively formed along a multi-station stamping line to indicate acceptability of the stamped part.
Different diameter markers are placed in corresponding locations in each of the dies sets so that at the end of stamping circular marks formed on the part by the markers usually center together around a common point and form a "bulls eye" to indicate that the stamped part is made to specifications. In the event a part gets off location in any one or more of the die sets, the circles would become noticeably eccentric with respect to the planned center and may overlap. Since the different circles readily reveal which die set causes any overlap or substantial eccentricity, that die set can be adjusted or repaired as needed to correct die problems.
While circles are featured as the observable preferred markings, other geometric configurations, such as rectangles, triangles and line markings, or combinations thereof, or other shapes can now be readily used in place of circles to readily indicate die set accuracy or inaccuracy. Furthermore, while this invention has been generated to improve accuracy in the staged stamping of metal parts, plastics and composite materials may also be stamped or otherwise marked with the bottom marker tools and methods of this invention.
Another feature, object and advantage of this invention is to provide new and improved die structures and stamping methods involving the application of juxtaposition markings on parts being stamped in various stamping stations that accumulate and visually indicate whether of not a part being stamped is within specification and, if not, which of the stations is causing inaccuracy in the stamping so that such stations can be readily repaired.